Laplace's Demon
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In the
history of science The history of science covers the development of science from ancient history, ancient times to the present. It encompasses all three major branches of science: natural science, natural, social science, social, and formal science, formal. Pr ...
, Laplace's demon was a notable published articulation of causal determinism on a scientific basis by
Pierre-Simon Laplace Pierre-Simon, Marquis de Laplace (; ; 23 March 1749 – 5 March 1827) was a French polymath, a scholar whose work has been instrumental in the fields of physics, astronomy, mathematics, engineering, statistics, and philosophy. He summariz ...
in 1814. According to determinism, if someone (the demon) knows the precise
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and
momentum In Newtonian mechanics, momentum (: momenta or momentums; more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. ...
of every particle in the universe, their past and future values for any given time are entailed; they can be calculated from the laws of
classical mechanics Classical mechanics is a Theoretical physics, physical theory describing the motion of objects such as projectiles, parts of Machine (mechanical), machinery, spacecraft, planets, stars, and galaxies. The development of classical mechanics inv ...
.


English translation

This intellect is often referred to as ''Laplace's demon'' (and sometimes ''Laplace's Superman'', after
Hans Reichenbach Hans Reichenbach (; ; September 26, 1891 – April 9, 1953) was a leading philosopher of science, educator, and proponent of logical empiricism. He was influential in the areas of science, education, and of logical empiricism. He founded the ''G ...
). Laplace himself did not use the word "demon", which was a later embellishment. As translated into English above, he simply referred to: ''"Une intelligence ... Rien ne serait incertain pour elle, et l'avenir, comme le passé, serait présent à ses yeux."'' This idea seems to have been widespread around the time that Laplace first expressed it in 1773, particularly in France. Variations can be found in Maupertuis (1756),
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(1768),
Baron D'Holbach Paul Thiry, Baron d'Holbach (; ; 8 December 1723 – 21 January 1789), known as d'Holbach, was a Franco-German philosopher, encyclopedist and writer, who was a prominent figure in the French Enlightenment. He was born in Edesheim, near Landau ...
(1770), and an undated fragment in the archives of
Diderot Denis Diderot (; ; 5 October 171331 July 1784) was a French philosopher, art critic, and writer, best known for serving as co-founder, chief editor, and contributor to the along with Jean le Rond d'Alembert. He was a prominent figure during t ...
. Recent scholarship suggests that the image of a super-powerful calculating intelligence was also proposed by Roger Joseph Boscovich in his 1758 ''Theoria philosophiae naturalis''.


Arguments against Laplace's demon


Thermodynamic irreversibility

According to chemical engineer Robert Ulanowicz in his 1986 book ''Growth and Development'', Laplace's demon met its end with early 19th century developments of the concepts of irreversibility,
entropy Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the micros ...
, and the
second law of thermodynamics The second law of thermodynamics is a physical law based on Universal (metaphysics), universal empirical observation concerning heat and Energy transformation, energy interconversions. A simple statement of the law is that heat always flows spont ...
. In other words, Laplace's demon was based on the premise of reversibility and classical mechanics; however, Ulanowicz points out that many thermodynamic processes are irreversible, so that if thermodynamic quantities are taken to be purely physical then no such demon is possible as one could not reconstruct past positions and momenta from the current state. Maximum entropy thermodynamics takes a very different view, considering thermodynamic variables to have a statistical basis which is separate from the deterministic microscopic physics. However, this theory has met criticism regarding its ability to make predictions about physics; a number of physicists and mathematicians, including Yvan Velenik of the Department of Mathematics for the
University of Geneva The University of Geneva (French: ''Université de Genève'') is a public university, public research university located in Geneva, Switzerland. It was founded in 1559 by French theologian John Calvin as a Theology, theological seminary. It rema ...
, have pointed out that maximum entropy thermodynamics essentially describes our knowledge about a system but does not describe the system itself.


Quantum mechanical irreversibility

Due to its canonical assumption of
determinism Determinism is the Metaphysics, metaphysical view that all events within the universe (or multiverse) can occur only in one possible way. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes ov ...
, Laplace's demon is incompatible with the
Copenhagen interpretation The Copenhagen interpretation is a collection of views about the meaning of quantum mechanics, stemming from the work of Niels Bohr, Werner Heisenberg, Max Born, and others. While "Copenhagen" refers to the Danish city, the use as an "interpretat ...
, which stipulates indeterminacy. The interpretation of quantum mechanics is still very much open for debate and there are many who take opposing views (such as the many worlds interpretation and the de Broglie–Bohm interpretation).


Chaos theory

Chaos theory Chaos theory is an interdisciplinary area of Scientific method, scientific study and branch of mathematics. It focuses on underlying patterns and Deterministic system, deterministic Scientific law, laws of dynamical systems that are highly sens ...
is sometimes pointed out as a contradiction to Laplace's demon: it describes how a deterministic system can nonetheless exhibit behavior that is impossible to predict: as in the butterfly effect, minor variations between the starting conditions of two systems can result in major differences. While this explains unpredictability in practical cases, applying it to Laplace's case is questionable: under the strict demon hypothesis all details are known—to infinite precision—and therefore variations in starting conditions are non-existent. Put another way: Chaos theory is applicable when knowledge of the system is imperfect, whereas Laplace's demon assumes perfect knowledge of the system, therefore the variability leading to chaos in chaos theory and non-variability in the knowledge of the world Laplace's demon holds are noncomparable.


Cantor diagonalization

In 2008, David Wolpert used Cantor diagonalization to challenge the idea of Laplace's demon. He did this by assuming that the demon is a computational device and showed that no two such devices can completely predict each other. Wolpert's paper was cited in 2014 in a paper of Josef Rukavicka, where a significantly simpler argument is presented that disproves Laplace's demon using Turing machines, under the assumption of free will.


Additional context

In full context, Laplace's demon, as conceived, is infinitely removed from the human mind and thus could never assist humanity's efforts at prediction: Despite this, the English
physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...
Stephen Hawking Stephen William Hawking (8January 194214March 2018) was an English theoretical physics, theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge. Between ...
said in his book '' A Brief History of Time'' that "Laplace suggested that there should be a set of scientific laws that would allow us to predict everything that would happen in the universe." Similarly, in James Gleick's book '' Chaos'', the author appears to conflate Laplace's demon with a "dream" for human deterministic predictability, and even states that "Laplace seems almost buffoon-like in his optimism, but much of modern science has pursued his dream" (pg.14).


Loschmidt's paradox

Recently, Laplace's demon has been invoked to resolve a famous paradox of statistical physics, Loschmidt's paradox. The argument is that, in order to reverse all velocities in a gas system, measurements must be performed by what effectively becomes a Laplace's demon. This, in conjunction with Landauer's principle, allows a way out of the paradox.


Recent views

There has recently been proposed a limit on the computational power of the universe, i.e. the ability of Laplace's demon to process an infinite amount of information. The limit is based on the maximum entropy of the universe, the speed of light, and the minimum amount of time taken to move information across the Planck length, and the figure was shown to be about 10120 bits. Accordingly, anything that requires more than this amount of data cannot be computed in the amount of time that has elapsed so far in the universe. A simple logical proof of the impossibility of Laplace's idea was advanced in 2012 by Iegor Reznikoff, who posits that the demon cannot predict his own future memory..


See also

* Clockwork universe theory *
Eudaemons The Eudaemons were a small group headed by graduate physics students J. Doyne Farmer and Norman Packard at the University of California Santa Cruz in the late 1970s. The group's immediate objective was to find a way to beat roulette using a conce ...
* Evil demon * ''Laplace's Witch'' (film) * ''Laplace's Angel'' (song) * Maxwell's demon *
Omniscience Omniscience is the property of possessing maximal knowledge. In Hinduism, Sikhism and the Abrahamic religions, it is often attributed to a divine being or an all-knowing spirit, entity or person. In Jainism, omniscience is an attribute that any ...
* Superdeterminism


References

{{DEFAULTSORT:Laplace's Demon Determinism Thought experiments Pierre-Simon Laplace Fictional demons